For a scientific study I plan to assess balance parameters with the Wii Balance Board. The idea is to collect data from the Balance Board while a subject is playing a game on the Nintendo Wii software (e.g. skiing, snowboarding,..). Therefore the data generated by the Balance Board has to go to a PC and the Wii console at the same time. How is this possilbe?I am very happy for any advice that enables me to do this :-)

I have been able to use two programs running side by side on one PC to communicate independently with one wiimote, using one bluetooth dongle.

With a PC and Wii it may be a different situation. See if you can pair the balanceboard (essentially a wiimote) with both a PC and a Wii at the same time. I do not know if the bluetooth protocol allows this.

If so, the PC could run a program like glovepie to obtain the controller status.

Reading data from the controller should be straightforward, however writing or overwriting data on the controller could cause conflicts with the wii.

Also, some data written to the control registers of the controller cannot be read back. So if the Wii sets some unreadable control register then glovepie or other sniffer program won't be able to detect it.